Numerical display device having filamentary light sources

ABSTRACT

A display device is provided of the type comprising a plurality of electrical resistance filamentary light sources so arrayed that when various combinations of the sources are selectively energized, various luminous symbols are produced. The filaments lie in a common plane and do not cross one another, and are disposed to form a substantially closed figure having corners. End portions of several of the filaments extend beyond the corners of the figure, and remain non-luminous when central portions of these filaments are luminous.

ilnited States Patent Lindburg et al.

[54] NUMERICAL DISPLAY DEVICE HAVING FILAMENTARY LIGHT SOURCES [75] Inventors: Norman Lee Lindburg, Berkeley Heights; Richard Arthur Bonnette, New Providence; Thomas Edward Deegan, Winding Way, Belle Mead, all of NJ.

[73] Assignee: RCA Corporation, New York, NY.

[22] Filed: Apr. 29, 1969 [21] Appl. No.: 820,185

[52] U.S. Cl. ..'...3l3/l09.5, 313/315, 313/316 [51] Int. Cl ..H01j 61/66, HOlk 7/04 [58] Field ofSearch ..3l3/109.5,315,3l6

[5 6] References Cited UNITED STATES PATENTS 2,878,418 Garfinkel et al ..3l5/69 [4 1 June 5,1973

Demarest et al. 313/1095 Carley ..313/l09.5

Primary Examiner-John Kominski Attorney-G. H. Bruestle [57] ABSTRACT A display device is provided of the type comprising a plurality of electrical resistance filamentary light sources so arrayed that when various combinations of the sources are selectively energized, various luminous symbols are produced. The filaments lie in a common plane and do not cross one another, and are disposed to form a substantially closed figure having corners. End portions of several of the filaments extend beyond the corners of the figure, and remain non-luminous when central portions of these filaments are luminous.

6 Claims, 5 Drawing Figures 39 DH J P E 5 v 3, 737, 706

A: a YEN TORS '9- '9- Nor LeeL/ndburg, Y PRIOR ART PRIOR ART Hi 0rd Arthur 8 mile,

and Thomas Edwar egan.

ITYDRNEY NUMERICAL DISPLAY DEVICE HAVING FILAMENTARY LIGHT SOURCES BACKGROUND OF THE INVENTION is mounted between a pair of support means which also serve as electrical terminals for the filaments. The support means inherently serve as heat sinks for the filaments, whereby end portions of the filaments are maintained non-luminous when central portions of the filaments are luminous. Also, to prevent shorting together of various ones of the support means, or shorting together of various ones of the filaments, which are un coated for greater lighting efficiency, appropriate minimal spacings are provided between the various support means and filaments. These factors of non-luminous filament end portions and minimal spacings between the elements of the device give rise to problems of providing readily identifiable symbols having uniform dimensions from symbol to symbol, and providing display devices having wide viewing angles.

SUMMARY OF THE INVENTION A display device is provided comprising a plurality of rectilinear, non-intersecting, electrical resistance filaments lying in a substantially common plane. A first filament has an end portion which is adjacent to a second filament and which extends therebeyond. The second filament has an end portion which is adjacent to the first filament but which terminates short thereof. Means are provided to render the end portion of the first filament non-luminous when a central portion of the first filament is luminous.

DESCRIPTION OF THE DRAWING FIG. 1 is a section view of a novel display device showing the light sources thereof;

FIG. 2 is a partial section of the device shown in FIG. 1 taken along the line 2-2 of FIG. 1;

FIG. 3 is a section view, partly broken away, of the device showing the rear connections to the light sources thereof; and

FIGS. 4 and 5 are schematic drawings illustrating the arrangement of the light sources in certain prior art devices.

DESCRIPTION OFPREFERRED EMBODIMENTS OF THE INVENTION With reference to FIGS. I and 2, a display device is shown which comprises a transparent glass envelope 12 of a type well known in the electron tube arts. The envelope [2 includes a stem 14 having a plurality, e.g., nine, through leads 16. mounted on the leads within the envelope is a thin, flat substrate 26, of, for example, an alumina ceramic having a dark and dull surface to minimize light reflection.

Extending through the substrate 26, in bonded relation therewith, are a plurality of support elements or posts 28. Mounted between pairs of posts 28 on the front side, as viewed in FIG. 1, of the substrate 26 are a plurality of rectilinear electrical resistance filaments 30, 31, 32, 33, 34, 35, and 36. In this embodiment, the

filament each comprise an elongated coil of refractory wire.

By selectively energizing various ones of the filaments, that is, by applying a voltage between the pairs of posts 28 between which the selected filaments are mounted, various luminous images or symbols, numerals, in the instant embodiment, are obtained. For example, an image of the numeral 2 is obtained by lighting the filaments 30, 35, 31, 34, and 32, each filament providing an elongated element or segment of the composite image.

To minimize the number of leads 16 required for the device, one post 28 of each pair of posts connected to each filament is connected to a common lead 16. The other post 28 of each pair of posts, as shown in FIGS. 2 and 3, is connected, on the back side of the substrate 26, to a different one of the leads 16, whereby energizing voltages can be selectively applied to individual ones of the various filaments.

To minimize the number of posts 28'used, as well as to reduce the spacing between theluminous vertical segments of the numerals, an end of each filament 33 and 34, and an end of each filament 35 and 36, are mounted on common posts, designated as 28.

For various reasons, such as for low cost, reduced warm-up time, greater lighting efficiency, and the like, the various filaments 30 through 36, inclusive, are uncoated. To prevent shorting together of the filaments, which lie in a substantially common plane, for a reason described hereinafter, the filaments do not cross one another.

Prior art filament arrangements, as shown in US. Pat. Nos. 3,408,523 issued Oct. 29, 1968, to P. C. Demarest, and 3,416,020, issued Dec. 10, 1968, to J. A. Carley, are shown in FIGS. 4 and 5, respectively.

In the filament arrangement shown in FIG. 4, the filaments 38 cross one another near the ends thereof. A result of this is that the end portions of the filaments, rendered non-luminous owing to the heat sinking provided by the filament support posts 39, are disposed beyond the intersections of the filaments, whereby the corners of the numerals provided by intersecting filaments are fully luminous. A disadvantage of this construction, however, is that there is a danger of the filamentary coils snagging one another during assembly of the device, or even in operation of the device upon mechanical shock thereto and resulting vibration of the filaments. Also, to prevent shorting together of the various crossed filaments, the filaments are disposed in spaced apart planes. Although the FIG. 4 prior art arrangement provides for a small spacing between filaments to provide a wide viewing angle of the device, the viewing angle is nevertheless restricted by the fact that at wide angles, e.g., in excess of inclusive, the spacing between the filament planes becomes visible, thereby distorting the appearance of the luminous symbol.

In the prior art filament arrangement shown in FIG. 5, the filaments can all lie in a common plane, since at the points of intersection of the filaments, that is points D, B, and .l, the filaments are electrically connected. A disadvantage of this filament arrangement, however, is that numerals having different heights are provided by the device. In applications where the devices are used in a side by side array to provide a plural digit number or legend, the different height numerals tend to impair, or at least delay, recognition of the composite legend.

The different height numerals are caused by two factors, as follows.

To prevent shorting together of the different support posts for the filaments, various posts, i.e., A and C, and H and l, are spaced from one another at the corners of the array of filaments. The posts B and J, on the other hand, which are each common to two filaments, are disposed at the corners of the array of filaments. Thus, the numeral 6, for example, formed by the lighting of the filaments CD, DH, 11, G], and DE, has a shorter height than the numeral 7 formed by the lighting of the filaments AB, BF, and GJ.

Secondly, owing to the heat sinking of the filaments by the support posts, end portions of the energized luminous filaments remain non-luminous. Thus, the numeral 7, for example, has a luminous height somewhat less than the distance between the posts B and J owing to the non-luminous portion of the filament GJ adjacent to thepost J. The numeral 8, on the other hand, formed by the lighting of all the filaments, has a height equal to the distance between the posts 8 and J.

The problems of both these prior art filament arrangements are solved in the instant embodiment, as follows.

Because the filaments do not cross one another at points where they are electrically isolated, the filaments are disposed in a substantially common plane. This provides for a device wide viewing angle, e.g., 140, inclusive, and reduces the possibility of snagging of the filaments with'one another.

The posts 28, which are each common to two filaments, are not disposed adjacent to corners of the array of filaments, as is the case in the FIG. prior art filament arrangement, but are disposed remote from the corners of the filamentary array. In this arrangement, the presence of the common posts 28' does not give rise to differences in the heights of the various numerals produced by the device. I

The effect of the non-luminous filament end portions on the heights of the numerals is avoided as follows. The six filaments 30, 32, 33, 34, 35, and 36 are disposed along the sides of a figure, a rectangle in this embodiment. Stated in other words, the filament 30 ex tends along the directions 40 (indicated by dashed lines in FIG. 1), the filament 32 extends along the directions 42, the filaments 33 and 34 extend along the directions 44, and the filaments 35 and 36 extend along the directions 46, the directions 40, 42, 44, and 46 intersecting to form a rectangle.

The two filaments 30 and 32, which provide horizontal segments of numerals, e.g., the upper and lower bars of the numeral 2, are disposed along the rectangle sides defined by the directions 40 and 42, and terminate short of the corners of the rectangle. The four filaments 33, 34, 35, and 36, which provide vertical segments of numerals, e.g., the vertical sides of the numeral eight, are disposed, two to a side, along the rectangle sides defined by the directions 44 and 46. An end portion 50 of each filament 33, 34, 35, and 36 extends beyond each corner of the rectangle.

In operation of the device, various ones of the filaments are rendered luminous by applying an energizing voltage across the filaments. As noted, the support posts 28 serve as heat sinks for the filaments, whereby end portions of the filaments remain non-luminous. As a practical manner, using fine, e.g., less than 1 mil diameter electrical resistance wire for the filaments, and

comparatively massive support posts, e.g., having a di-' ameter in excess ofa few mils, the posts serve as infinite capacity heat sinks for the filaments, and the length of the non-luminous end portions of the filaments is determined entirely by the dimensions and physical properties of the filament coils.

The line of demarcation between the luminous and non-luminous portions of the filaments is relatively sharp. The filaments are so designed and arrayed relative to one another that the extending end portions 50 of the filaments 33, 34, 35, and 36 remain nonluminous when central portions of these filaments are luminous, the demarcations between the non-luminous end portions 50 and the luminous central portions being disposed substantially at the corners of the rectangular array of filaments.

As a result of this arrangement, all the numerals'produced by the device have a uniform height, i.e., equal to the distance between the horizontal filaments 30 and 32.

By way of example, each of the filaments 30 through 36, inclusive, is formed from a wire having a diameter of 0.4 mil, the wire being wound into a coil having an outer diameter of 2.0 mils. The wire comprises an alloy of 3 percent rhenium, balance tungsten, by weight. The filaments 33, 34, 35, and 36 have a length of 3l2 mils, the filament coils containing about 577 turns to the inch. The filaments 30, 31, and 32 have a length of 286 rnils,'the filament coils containing about 630 turns to the inch. The support posts 28 comprise rods of an alloy comprising 17 percent cobalt, 29 percent nickel, and 54 percent iron, by weight, having the tradename Kovar, the rods having a length of 250 mils and a diameter of 10 mils. The end portions 50 of the filaments 33, 34, 35, and 36 have a length of 22 mils.

In display devices having dimensions substantially different from the specific embodiment described herein, the dimensions of the support posts may effect the length of the non-luminous filament end portions. Providing the proper relationship between posts and filaments to provide the desired non-luminous end portions 50, however, is within the skill of workers in the field.

What is claimed is:

l. A display device having a plurality of rectilinear electrical resistance filaments arranged to permit selectively exciting said filaments to create luminous symbols;

first and second ones of said filaments being disposed substantially co-planar, and non-intersecting relative to each other;

said first filament having an end portion adjacent said second filament which extends beyond said second filament;

said second filament having an end portion adjacent said first filament which terminates short of said first filament; and A means for rendering said first filament end portion non-luminous when a central portion of said first filament is luminous.

2. A display device comprising:

a plurality of rectilinear, non-intersecting, electrical resistance filaments lying in a substantially common plane;

said filaments extending in directions which are intersecting;

sink means comprises a combination mechanical support and electrical terminal means for said another filament.

4. A display device as in claim 2 wherein said filament directions form a substantially closed figure;

each of said filaments being disposed along a side of said figure; and

said end portion extends beyond said figure and forms no part thereof.

5. A display device comprising:

a plurality of rectilinear, non-intersecting, electrical resistance filaments lying .in a substantially common plane;

a plurality of elements serving as combination terminal support and heat sink means for said filaments,

different ones of said elements being connected to different ones of the ends of said filaments, whereby various combinations of said filaments can be selectively energized to provide luminous symbols;

said filaments being disposed along the sides of a substantially closed figure;

first filaments forming horizontal segments of said symbols being disposed along first sides of said figure between corners thereof and terminating short of said corners;

second filaments forming vertical segments of said symbols being disposed along second sides of said figure intersecting said first sides, said second filaments including end portions extending beyond the corners formed by the intersections of said first and second sides; and the elements connected to the extending end portions of said second filaments serving as heat sinks for said end portions, whereby said end portions remain non-luminous when central portions of said second filaments are luminous. 6. A display device as in claim 5 including two second filaments disposed along each of two second sides, the ends of said two filaments other than said extending ends being mounted on a common support element. 

1. A display device having a plurality of rectilinear electrical resistance filaments arranged to permit selectively exciting said filaments to create luminous symbols; first and second ones of said filaments being disposed substantially co-planar, and non-intersecting relative to each other; said first filament having an end portion adjacent said second filament which extends beyond said second filament; said second filament having an end portion adjacent said first filament which terminates short of said first filament; and means for rendering said first filament end portion non-luminous when a central portion of said first filament is luminous.
 2. A display device comprising: a plurality of rectilinear, non-intersecting, electrical resistance filaments lying in a substantially common plane; said filaments extending in directions which are intersecting; a first of said filaments extending in a first direction terminating short of an intersection of directions, another of said filaments extending in a second direction through said intersection, said another filament having an end portion extending beyond said intersection; and heat sink means connected to said end portion, said extending end portion being non-luminous when the central portion of said another filament is luminous, the demarcation between said end and central portions being substantially at said intersection.
 3. A display device as in claim 2 wherein said heat sink means comprises a combination mechanical support and electrical terminal means for said another filament.
 4. A display device as in claim 2 wherein said filament directions form a substantially closed figure; each of said filaments being disposed along a side of said figure; and said end portion extends beyond said figure and forms no part thereof.
 5. A display device comprising: a plurality of rectilinear, non-intersecting, electrical resistance filaments lying in a substantially common plane; a plurality of elements serving as combination terminal support and heat sink means for said filaments, different ones of said elements being connected to different ones of the ends of said filaments, whereby various combinations of said filaments can be selectively energized to provide luminous symbols; said filaments being disposed along the sides of a substantially closed figure; first filaments forming horizontal segments of said symbols being disposed along first sides of said figuRe between corners thereof and terminating short of said corners; second filaments forming vertical segments of said symbols being disposed along second sides of said figure intersecting said first sides, said second filaments including end portions extending beyond the corners formed by the intersections of said first and second sides; and the elements connected to the extending end portions of said second filaments serving as heat sinks for said end portions, whereby said end portions remain non-luminous when central portions of said second filaments are luminous.
 6. A display device as in claim 5 including two second filaments disposed along each of two second sides, the ends of said two filaments other than said extending ends being mounted on a common support element. 